Digital data streams, for example based on the MPEG2 Standard ISO/IEC 13818-1, are often broken down into packets. In this case, certain information items, such as time details, are contained only in specific packets. In particular, the cited standard defines the structure of a transport data stream (TS). An MPEG2-TS data stream is a packet-oriented stream which comprises successive transport packets (“Transport Stream Packets”, TSP). A TSP comprises a header and transport data, which in turn represent a part of a packet (PES packet) of a packet-oriented elementary data stream (Packetized Elementary Stream, PES). In order to obtain an entire PES packet, the individual parts must be extracted from successive associated TSPs and must be assembled without in the process changing the sequence of the TSPs. A PES packet comprises header information and a data field. The data field may, for example, be a part of a video data stream or of an audio data stream. In order to search through (scan) a data stream such as this for information, each packet must be investigated, which takes a long time. Furthermore, extensive evaluation processes may be required, for example error checking or error correction.